The Regulation of Unlicensed Sub-Ghz Bands: Are Stronger Restrictions Required for LPWAN-Based Iot Success?

1 The Regulation of Unlicensed Sub-GHz bands: Are Stronger Restrictions Required for LPWAN-based IoT Success? David Castells-Rufas, Adrià Galin-Pons, and Jordi Carrabina (like [4][5]) it comes implicit that a high percentage of them Abstract—Radio communications using the unlicensed Sub- will be connected by wireless links, as some of the GHz bands are expected to play an important role in the fundamental technologies enabling IoT are Low Power Wide deployment of the Internet of Things (IoT). The regulations of Area Networks (LPWAN) working on unlicensed bands, the sub-GHz unlicensed bands can affect the deployment of which are free to use. LPWAN networks in a similar way to how they affected the deployment of WLAN networks at the end of the twenty's Nevertheless, the use of the radio spectrum is regulated in century. This paper reviews the current regulations and labeling most countries of the world. This aspect is often overlooked in requirements affecting LPWAN-based IoT devices for the most the literature, not considering the limitations that regulation relevant markets worldwide (US, Europe, China, Japan, India, could impose on the deployment of such technologies. Our Brazil and Canada) and identify the main roadblocks for massive hypothesis is that current regulations can hamper the adaption of the technology. deployment of wireless IoT applications due to their impact on Finally, some suggestions are given to regulators to address the open challenges. the spectrum use and the microelectronics industries. The paper is organized as follows: we describe the radio Index Terms—Radio networks, Radio spectrum management, spectrum in Section II, and recall the events that shaped the Internet of things, Wireless sensor networks. current spectrum regulations in Section III. Section IV presents the different technologies in use in the IoT wireless I. INTRODUCTION landscape. Section V reviews the regulation and certification HERE are different predictions about the number of process on the main world markets. In Section VI we analyze Tdevices that will become connected to the internet in the what rules the regulators can enforce in trying to orchestrate near future with the widespread of the Internet of Things the spectrum. In Section VII we analyze the mathematical concept (IoT). Either being 50 G by 2020 [1], or 75 G by 2025 expressions that could describe the node density and bitrate [2], it seems to be a consensus about the disruptive nature of density of LPWAN. In Section VIII we estimate the IoT [3] and about the number of connected devices being in maximum values for LoRa and Sigfox technologies given on the order of billions. the scope of different regulations. Those results are contrasted The confluence of the evolution of many technologies like with the results from the literature in Section IX. In Section X energy scavenging, machine-to-machine communications, and we study additional economic impacts caused by the current low power wireless communication technologies support the regulation. In Section XI, before concluding, we discuss the narrative that any device that would benefit from being benefits of the harmonization of regulations. connected will definitely be connected since the cost of the connection will be insignificant. This cost includes the cost of II. RADIO-SPECTRUM LIMITS the chips, the cost of the communication channel, and the cost Although, theoretically, the radio spectrum is an infinite of the energy. resource, the interesting frequency bands for communication However, to the best of our knowledge, the studies in the over the earth surface are delimited by two factors: literature are not so explicit about predicting the number of devices that will be wirelessly connected through low power 1) In the low end, by the Shannon-Hartley theorem (Eq. 1), or low throughput radio communication links. In many works which relates the amount of information potentially transmitted over a channel. This work has been partly funded by the Serene-IoT project (Penta 16004). D. Castells-Rufas is with the Microelectronics and Electronic Systems 퐶 = 퐵 log 1+ (1) Department, Universitat Autònoma de Barcelona Bellaterra, 08193 Spain (e- mail: [email protected]). A. Galin-Pons is with R&D Department, Applus+ Laboratories, Where 퐶 is the traffic capacity of the channel in bits per Bellaterra, 08193 Spain (e-mail: [email protected]). second, is the bandwidth of the channel in Hertz and ⁄ is Jordi Carrabina is with the Microelectronics and Electronic Systems 퐵 S 푁 Department, Universitat Autònoma de Barcelona Bellaterra, 08193 Spain (e- the signal to noise ratio of the channel. So if we want to mail: [email protected]). 2 transmit an amount of information in a time period either we For certain frequencies and the appropriate atmosphere use enough bandwidth or we have enough signal to noise ratio. conditions the ionosphere contributes to allow what is known In this trade-off we have a limited ability to increase the signal as Skywave propagation, increasing the possible range to a to noise ratio of radio channels, it is easier to select the carrier much longer distance. frequencies that will provide enough bandwidth to allow the Figure 1 depicts a simplified model of the different effects required traffic capacity. that contribute to the cost of transmitting information from a sender to a receiver using different frequencies and different 2) In the high end, frequencies above PHz are known to be distances between both endpoints. ionizing radiation and harmful to human life, so they are This is a simple model with just two endpoints. Current avoided. Secondly antenna efficiency has an intrinsic communication systems are typically not so simple, and cost is attenuation relation with frequency, i.e. a reduction of the more complex to compute. The observed limitations have been received power (푃) with respect to the emitted power (푃). overcome by deploying networks of antennas and satellite- This is known as free space path loss (FSPL). Ignoring the based communications. In this context, there is not a single gain effects of both antennas the loss is described by Eq. 2, efficiency measure, but several, like spectrum efficiency (SE) where 푑 is the distance, 푓 the frequency, and 푐 the speed of or energy efficiency (EE) [6]. light. Nevertheless, since the radio spectrum is a scarce resource, it comes as no surprise that economic laws and policymakers play an important role to orchestrate its exploitation in an 퐹푆푃퐿 = = (2) attempt to maximize its utility. Moreover, different frequencies propagate differently in the III. BRIEF HISTORY OF RADIO SPECTRUM REGULATION atmosphere. Especially frequencies at the GHz ranges are Going back in history, after the discovery of the possibility absorbed by atmospheric gases such as O , H O, etc. 2 2 of transmitting information through electromagnetic waves, Another factor that influences the suitability of different radio was mostly used for Morse communication, but at the frequencies is the earth curvature, which limits the range of beginning with no regulation. Regulations were later direct line of sight propagation to a distance known as radio introduced in the Berlin 1903 and London 1912 conventions to horizon. The radio horizon is mainly determined by the height orchestrate different international radio services with an of the communicating antennas. important focus on emergency situations. An alternative propagation medium is the surface of the Shortly after the sinking of the Titanic, US adopted the earth. Ground wave propagation is possible below 3 MHz, but Radio Act of 1912, taking a leadership position that it would it is practically unfeasible to go further than some hundreds of maintain for the rest of the century. The main early kilometers. beneficiaries of the radio technology were still maritime ships. The International Telecommunication Union (ITU), an International Regulatory Body (IRB) had been founded previously, in 1865. Regional and International Regulatory Bodies (RRB and IRB) were playing an important role to ensure effective communications within different territories. National Regulatory Bodies (NRB) were still not needed because the technology was either controlled by governments or in hands of very few pioneers. The invention of the amplitude modulation (AM) and its application for voice transmission caused the introduction of commercial broadcast radio stations. Soon after the first commercial radio emission by KDKA in 1920, the number of transmitters, both commercial and amateur, proliferated at a fast pace creating a chaotic situation with thousands of amateur broadcasters and common interferences to commercial radio stations. The US government saw the need of licensing different radio bands and established transmission Figure 1 Illustrative simplified example of the transmission power that a transmitter should use so that a receiver endpoint can decode the signal power limits in the Radio Act US 1927 to solve the situation. depending on the frequency of the carrier and the distance of the receiving In the following decade many advances were made. endpoint assuming an antenna height of 200m, and -120 dBm of receiver Television [7] was improved and Television broadcasters sensitivity. For lower frequencies, surface wave propagation allows a long distance range. For higher frequencies the propagation is limited to the radio appeared slowly as new users of the radio spectrum. horizon, except in the Skywave band. For extremely high frequencies above Frequency Modulation [8] was invented as a better alternative 30GHz the absorption of the wave's energy by atmospheric gases limits the to AM thanks to its lower interference features. transmissions to very short distances. In this dynamic scenario the US government issued the Communications Act of 1934, which created the Federal 3 Communications Commission (FCC), a NRB to regulate the by free market forces and less driven by the command and radio spectrum in US. Regulators not only licensed control of governments. frequencies and regulated transmission power, but also introduced the mandatory use of communication standards in IV.

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